The scanning electron microscope can now be used to elucidate many molecular as well as morphological aspects of a variety of scientific projects. Six investigators having diverse research interests, but a common need for a scanning electron microscope capable of high-resolution backscatter detection, request a JEOL 840A. Their projects include 1) the structure and function of the connective tissue in heart muscle cells: 2) the cellular mechanism of action of antidiuretic hormone; 3) immune mediated inflam- mation and MHC expression in the central nervous system, particularly as it relates to myelin damage; 4) Staphylococcus aureus infection of endothelial tissue including the identification and distribution of specific membrane proteins which facilitate S. aureus adherence and subsequent endocytosis; 5) the mechanism of cyto adherence of Plasmodium falciparum to the vascular endothelium in malaria infection including the distribution of an 88Kd glycoprotein on infected erythrocytes, monocytes, platelets, endothelial cells and C32 melanoma cells. The features required by all investigators are a LaB6 electron gun to facilitate low voltage imaging, backscattered detection (specifically for detection of immunogold markers of surface proteins), microprocessor control of the electron optics, image summing, averaging and digitization utilizing a frame store buffer, and the ability to output video signals to video tape recorders for subsequent image analysis. All of the investigators are experienced electron microscopists who now need a current- generation scanning electron microscope to not only examine the morphology of their systems using secondary electron detection, but also require a high resolution backscatter detection for examining the localization and distribution of specific integral membrane proteins using immunogold labelling techniques. The institution encourages the use of shared facilities. An advisory committee, scheduling plan, staff, and the financial support of the facility is in place and functional. This instrument will be housed in the central electron microscope facility where it will be made available to the entire research community. There is currently no backscatter capability available at this institution.